Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual horário/posição para uma grade menor que 19, com menos de 21 voltas, e feita pela aprilia?
 ###Tabelas: CREATE TABLE 250cc_classification (250cc_classification_id AUTO_INCREMENT PRIMARY KEY, Rider VARCHAR, Manufacturer VARCHAR, Laps INT, Time/Retired VARCHAR, Grid INT) CREATE TABLE preliminary_competition (preliminary_competition_id AUTO_INCREMENT PRIMARY KEY, State VARCHAR, Interview INT, Swimsuit INT, Evening gown INT, Average INT) CREATE TABLE per_capita_gdp (per_capita_gdp_id AUTO_INCREMENT PRIMARY KEY, Economy VARCHAR, 1980 INT, Gap from Thailand as of 1980 (times) VARCHAR, 1985 INT, 1990 INT, 1995 INT, 2000 INT, 2005 INT, 2010 INT, 2012 INT, Gap from Thailand as of 2012 (times) VARCHAR, GDP as of 2012 after purchasing power parity (PPP) calculations (USD billions) VARCHAR, GDP per capita as of 2012 (PPP) INT) CREATE TABLE current_clubs_2014_season (current_clubs_2014_season_id AUTO_INCREMENT PRIMARY KEY, Club VARCHAR, Position in 2013 VARCHAR, First season INT, First season of current spell INT, Number of seasons in Superettan INT, Number of seasons in second tier INT) CREATE TABLE s-league (s-league_id AUTO_INCREMENT PRIMARY KEY, Match INT, Date VARCHAR, Home/Away VARCHAR, Opponent team VARCHAR, Score VARCHAR)  
SELECT Time/Retired FROM 250cc_classification WHERE Grid < 19 AND Manufacturer = aprilia AND Laps < 21